The invention concerns a diode network having at least one diode, which in operation is located in the path of a high-frequency signal, a predetermined diode voltage being applied to the diode to adjust its operating point.
To adjust the operating point of a diode in a signal-influencing network, current injection on the one hand and voltage injection on the other hand is known. An arrangement with current injection is shown in FIG. 2 of U.S. Pat. No. 5,210,633. In such an arrangement, the DC voltage applied to the diode varies in accordance with fluctuations in the level of the signal passed by the diode, which can be a high-frequency signal. In this known arrangement, if the diode network involves a predistorter circuit for linearising the output signal of an optical modulator, then the operating point can only be optimised for a single value of the amplitude of the high-frequency signal. Therefore, in the known arrangement, for optimum linearisation of the characteristic it is necessary to correct the current sources according to the amplitudes of the input signal.
Furthermore, U.S. Pat. No. 5,161,044, FIG. 15, discloses a diode network of the type initially described for linearising the output signal of an external optical modulator, by which the light leaving a light source is modulated. Here the terminals of two diodes in an inverse-parallel connection in the signal path of the signal to be influenced, are connected to voltage sources via inductors having a low ohmic resistance. The inductors are used to decouple the signal path from the voltage sources. A disadvantage of such an arrangement is that the inductors have stray capacitances, so that complete decoupling of the signal path from the voltage sources is not possible.